This invention relates to a method and means for eliminating radar interference signals and especially for eliminating short-pulse interference signals in the presence of continuous-noise jamming signals.
Coherent sidelobe cancellers used with omnidirectional antennas have the capability of aligning a null in the side-lobes of the antenna pattern with the direction from which a noise signal is being received and therefore cancelling out the noise. However, the canceller loops are too sluggish to place nulls in the sidelobe pattern of the antenna in the correct direction in time to cancel out short-pulse interference. Sidelobe blankers can be used to blank the radar when a pulse is received in the sidelobe of the main radar antenna by comparing the signal level in an omnidirectional antenna (hereinafter designated "omniantenna" or simply "Omni") with respect to the amplitude of the pulse in the main radar antenna. But if white-noise continuous jamming is present the radar will be totally blanked. This can be circumvented by placing cancellers in the Omni channel to cancel out the continous interference. This antenna system then becomes an interferometer and nulls may also be placed toward the source of the short-pulse interference. Therefore, the sidelobe blanker will not blank all the short-pulse interference it should.